Pigment concentrates for resins

ABSTRACT

Resinous pigment concentrates comprising at least one pigment and a dispersing additive of a naphthenic extender oil and/or a phosphate ester blended with a major portion of a resinous polymer containing a significant proportion of at least one polymerized conjugated diene monomer, when used for coloring resinous polymers as described, are effective in reducing such defects in finished articles as gels and surface blemishes.

This application is a divisional of application Ser. No. 829,053, filedFeb. 13, 1986, now U.S. Pat. No. 4,720,514, which is a divisional ofapplication Ser. No. 710,887, filed Mar. 11, 1985, now U.S. Pat. No.4,600,736.

This invention relates to pigment concentrates for blending inthermoplastic resin materials, and to processes for preparing coloredresin compositions.

BACKGROUND OF THE INVENTION

Pigment concentrates for blending in thermoplastic resins are known.Such concentrates must be selected according to the characteristics ofthe resins to be colored. It is desirable to avoid defects in coloredresins, particularly those which are transparent or translucent. Forexample, certain polymodal branched block copolymers of butadiene andstyrene are disclosed in my previous U.S. Pat. No. 3,939,112 (1976).These resinous copolymers, marketed by the Phillips Petroleum Company asK-Resin® resins, have many desirable properties, one of which is opticalclarity.

It is often desired to provide coloration to articles made from suchresins while still maintaining transparency, though opaque or"semi-opaque" colored articles made from various resins are also usefulin many applications. In any case, a well known convenient method ofproviding colored thermoplastic compositions is to employ a pigmentconcentrate or masterbatch wherein a pigment or colorant at relativelyhigh concentration is admixed with a polymer which is highly compatiblewith the thermoplastic resin to be colored. For example, polystyrene, asthe polymer to prepare the pigment concentrate, does not harm thetransparency of the final blend of compositions based upon suchpolymodal branched block copolymers, but the physical properties such asimpact strength are significantly reduced. To ensure compatibility, itwould be highly desirable to employ a similar polymer to prepare thepigment concentrate to be further blended or "let down" with the basepolymer.

Thus, it is desirable to develop pigment concentrates comprisingresinous polymers or similar resins which can be admixed with a majorportion of the same, a similar or related resin without creating theproblems such as defects in esthetic appearance or physical properties.

Problems have been encountered in attempting to use certain polymodalbranched block copolymers in pigment concentrates for coloring simialrpolymers. Primarily, gels or opaque surface blemishes are generated inthe final articles. In addition, agglomerates of pigment particles whichhave not been well dispersed often appear and mar the appearance of thefinal articles. Akin to the agglomerate problem is the problem ofstreaking wherein the final article shows streaks of heavier or lightercoloration. Streaking is generally an undesirable feature in the finalarticles. These defects are particularly conspicuous and objectionablein clear colored resins, which are a significant application of K-Resin®resins and similar polymodal copolymers.

Possible explanations for the above problems are as follows: (1) Gelsare caused by the high shear conditions needed to obtain a reasonablyhomogeneous blend of the pigment and resin in the concentrate; (2)Pigment agglomerates result from poorly dispersed pigment which in turnmight result from inadequate mixing in preparing the concentrate; and(3) Streaks are believed to result from inadequate mixing of the pigmentconcentrate with the virgin polymer.

The instant invention provides a means to reduce the occurrence of theabove problems in producing colored articles of various resinouspolymers, such as polymodal resinous copolymers or similar resins by theuse of certain additives in preparing a resinous pigment concentrate.

An object of this invention is to provide a resinous pigment concentratewhich can be used to produce colored resinous copolymers or similarresins without adverse effects as described above. Another object ofthis invention is a process for preparing such a resinous pigmentconcentrate. Still another object is a process for coloring resinouscopolymers or similar resins by admixing a base resin with the inventiveresinous pigment concentrate. A further object of this invention is aprocess for producing articles of resinous copolymers or similar resinscolored with the inventive pigment concentrate.

Other objects, advantages and features of the instant invention will beapparent from the following disclosure and the appended claims.

SUMMARY OF THE INVENTION

In accordance with this invention, it has been found that by preparing aresinous pigment concentrate by admixing a liquid dispersing additivewith a resinous copolymer containing significant amounts of apolymerized conjugated diene monomer, preferably in the range of fromabout 5 to about 40 weight percent, and a pigment, the problemsencountered in using such a resinous pigment concentrate can besignificantly reduced. For the purposes of this application "resinous"is taken to mean non-elastomeric.

Materials useful as said liquid dispersing additives are:

(A) Naphthenic type petroleum oils, also known as naphthenic extenderoils because of their longtime use in the rubber compounding art asrubber extenders; and

(B) Partial esters of phosphoric acid.

These dispersing additives can be used singly or in combination in asingle pigment concentrate, and pigment concentrates containing one orboth types of additives can be used in combination in colored resins.

In an embodiment, a pigment concentrate comprises a resin as describedabove, pigment, and a partial ester of phosphoric acid as the dispersingadditive. In another embodiment, the dispersing additive furthercomprises a naphthenic extender oil. In a preferred embodiment, theconcentrate comprises the resin, at least about 0.01 weight percent ofpigment, and about 0.5 to less than about 2 weight percent naphthenicextender oil, based on the total pigment concentrate. In still anotherembodiment, the concentrate comprises the resin, at least about 2 weightpercent of pigment, and about 2 to about 12 weight percent naphthenicextender oil.

Generally, it is most convenient and economical to use only one type ofsuch additives. The choice of the preferred additive may be influencedby factors comprising additive price, compatibility with pigments, andrequirements imposed by governmental agencies such as the Food and DrugAdministration (FDA). For example, the esters are presently preferredfor many applications because their use has been approved by the FDA.

While the pigment concentrate of this invention has been developed foruse with the K-Resin® resins disclosed in e.g., U.S. Pat. Nos. 3,939,112and 3,639,517 assigned to Phillips Petroleum Co., similar concentratescan be prepared for use with other resinous, linear or branched, block,butadiene/styrene copolymers, by blending pigments with a portion of theparent resins and a dispersing additive as disclosed herein. Thisinvention is generally applicable to resinous copolymers which containpolymerized conjugated diene monomers in proportions in the range offrom about 5 to about 40 weight percent, preferably from about 10 toabout 30 weight percent based on the total resin composition. Pigmentconcentrates of this invention can also be used for coloring otherresinous polymers such as polystyrene, polypropylene, and also forcoloring rubbery polymers such as butadiene, butadiene-styrenecopolymers and the like.

DETAILED DESCRIPTION OF THE INVENTION

The resinous pigment concentrate of this invention can be prepared byfirst adding an effective amount of a dispersing additive comprising anaphthenic oil, a partial ester of phosphoric acid, or a mixturethereof, to a suitable quantity of a suitable resin, then adding asuitable quantity of pigment, all under intensive mixing conditions. Aneffective amount of the dispersing additive for the preparation of theresinous pigment concentrate is that amount which will produce a pigmentconcentrate which is useful in normal concentrations for coloring resinswithin the scope of this invention, at the same time reducing theformation of gels, blemishes or the like in finished articles producedfrom the resultant colored resin. Preferably, the dispersing additive isincluded in the concentrate in an amount effective to essentiallyeliminate such gels and blemishes when the concentrate is added toresins in normal amounts. By using such a resinous pigment concentrate,resinous copolymers or similar resins can thus be colored by dispersingpigment completely and homogeneously through the resin compositionwithout reducing such important properties as impact strength. The useof an effective amount of the dispersing additive also allows the use ofsuch a resinous pigment concentrate without significant problems such asgel formation or blemishes in finished articles produced from theresultant colored resin, whether clear, semi-opaque, or opaque.

While not wishing to be bound by such theory, it is believed that theprincipal problem resolved by this invention, i.e., the formation ofgels in the resinous pigment concentrate and final resin compositions,is due to the sensitivity of the polymers to thermal or oxidativedegradation under relatively high shear mixing conditions due to thepresence of residual olefinic unsaturation derived from the polymerizedconjugated diene monomers. Thus, the problems would be expected toincrease in severity as the conjugated diene content of the resinincreases.

Use of Resinous Pigment Concentrate

The resinous pigment concentrate of the instant invention is employed inthe conventional manner known in the art. For example, the resinouspigment concentrate pellets and virgin resin pellets can be mixed in adrum tumbler mixing device at the desired ratios and the mixture thencharged to an extruder for fluxing of the blend to form an essentiallyhomogenous melt of colored resin composition for further processing asin injection molding or blow molding, or in forming colored pellets forstorage until ready for use in injection molding or blow moldingoperations. The pigment concentrate can be used as an amount in therange of from about 0.5 weight percent to about 25 weight percent of thefinal colored resin composition, depending upon the color strength ofthe concentrate, the intensity of color desired in the resincomposition, and whether the colored resin composition is to be clear,translucent, or opaque.

Suitable Additives

As discussed earlier, the amount of dispersing additive required in theresinous pigment concentrate is that which is effective in reducing theformation of gels, blemishes and the like when finished articles areproduced from resin compositions colored with suitable quantities ofsaid pigment concentrate, at the same time avoiding significantdegradation of physical properties. Enough dispersing additive should bepresent to disperse the pigment effectively in the concentrate, and,later, the resin to be colored, without any degradation of the polymer;however, excesses should be avoided, as this may prevent the developmentof enough internal shear on mixing for proper dispersion of the pigment.

The amount of the partial ester of phosphoric acid, or mixtures thereofwith naphthenic oil, employed in preparing the resinous pigmentconcentrate according to this invention can be broadly from about 0.5 toabout 12 percent by weight, based on the total resinous pigmentconcentrate composition.

The largest amounts of pigment are used in pigment concentrates whichare to be used in preparing colored opaque or semi-opaque resins, wheregels and some blemishes are less noticeable in finished products. Forsuch pigment concentrates, the amount of dispersing additive used can bein the range of from about 4 to about 12 weight percent of theconcentrate, or preferably in the range of from about 5 to about 10weight percent, depending upon the nature of the pigments and the baseresin which the concentrate is to be used to color. Pigment concentratesfor use in the preferred clear resins can contain dispersing additivesas in the range of from about 0.5 to about 10 weight percent, preferablyin the range of about 1 to about 6 weight percent, or more preferably,in the range of about 2 to about 4 weight percent based on the totalpigment concentrate.

Selections of values from within these ranges will depend upon suchfactors as the characteristics of the pigments, and the resins to beused in both the pigment concentrate and the colored composition.

A preferred pigment concentrate comprises as a dispersing additive anaphthenic oil alone in an amount in the range of from about 0.5 to lessthan about 2.0 weight percent of the pigment concentrate, which containsat least about 0.1 weight percent pigment. Another preferred concentratecomprises pigment as at least about 2 weight percent, and about 2 toabout 12 weight percent naphthenic oil.

Naphthenic Extender Oils

Naphthenic extender oils useful in accordance with this inventioncomprise naphthenes or paraffins and some aromatic hydrocarbons. Thenaphthenic extender oils such as conventionally employed in rubberformulations can be used for the practice of this invention. These oilshave a viscosity in the range of about 100 to about 5,000 SUS at 100° F.In a presently preferred embodiment, such oils contain about 40 weightpercent naphthenics, about 45 weight percent paraffins, and about 15weight percent aromatics. A particular preferred naphthenic extender oilis ASTM D-2226 Type 103, having a viscosity of 760 SUS at 100° F., aflash point of 410° F. and an aniline point of 179° F., marketed asSunthene®380 by the Sun Oil Co.

Naphthenic extender oils are preferred as the liquid dispersingadditives of certain embodiment of this invention because such oils arecompatible with the much larger amounts of naphthenic oils which can beadded to certain polymodal resins in amounts effective to improve impactstrength in accordance with my previous U.S. Pat. No. 3,939,112; thuswhen the resinous pigment concentrate is blended into the base resin,the naphthenic oil in the pigment concentrate can enhance theimprovement in impact strength of articles formed from the resin. Also,such naphthenic oils are readily available at reasonable cost in a widerange of viscosities which are effective for practicing this invention.

While a naphthenic extender oil can be added to such resins as at leastabout 10 weight percent of the resin composition to achieve asignificant increase in impact strength, such oils are generally addedto resins as only about 0.5 to about 10 weight percent to form thepigment concentrates of this invention. Thus, for example, when suchpigment concentrates are added to resin compositions as less than about20 weight percent, the extender oil included as part of said pigmentconcentrate will constitute less than 2 weight percent of said resincomposition.

Phosphate Esters

Alternatively, partial esters of phosphoric acid, chemically describedas free acids of complex organic phosphate esters, can be used as theliquid additive. While presently more expensive than the naphthenicoils, these materials are preferred for certain applications involvingfood packaging which require Food and Drug Administration (FDA) approvalof materials. Exemplary additives are marketed by GAF, Inc. asantistatic agents under the tradenames GAFSTAT®AD-510, AE-6109, AS-610and AS-710. Such products have significant lubricating and dispersingproperties which are believed to make them effective in formulating thepigment concentrates of this invention.

The product used in preparing pigment concentrates in Example I hereinwas GAFSTAT®AE-610, which is the reaction product of P₂ O₅ with thecondensation product of ethylene oxide (10 mole parts) and nonylphenol(1 mole part) at a ratio of 217 moles of the condensation product permole of P₂ O₅. Many such partial esters of phosphoric acid can beemployed as additives for preparing pigment concentrates for use withvarious resins as disclosed herein. Such phosphate esters are disclosedin U.S. Pat. No. 3,341,343 (1967) assigned on its face to GeneralAniline & Film Corp. of New York City.

Additives useful in this invention can be phosphate esters selected fromthe group consisting of mono-, diesters, triesters and mixtures thereofof phosphoric acid with a nonionic surfactant condensation product of anorganic compound containing at least 6 carbon atoms and containing areactive hydrogen with at least 1 mole of alkylene oxide.

The phosphate esters derived from nonionic surfactants (surface activeagents) are useful in the preparation of dispersions of compositions ofmatter of hydrophobic polymers. Phosphate esters have a number ofadvantages in this particular application. Their hydrophobic andhydrophilic nature may be varied over a wide range by the selection ofnonionic surfactants having varying amounts of alkylene oxides. This isa particular advantage when a dispersion of a pigment having a specifichydrophobic-hydrophilic balance is desired. The compatibility of themono and disubstituted esters may be further modified by conversion totheir salts. This is a distinct advantage in the formulation of thesecompositions.

Phosphate esters useful in attaining the objects of this invention areselected from the group corresponding to the general formula: ##STR1##wherein R is a residue of an alkyl, alkaryl or aryl compound having atleast 6 carbon atoms and a reactive hydrogen, e.g., the residue of analkylphenol, aliphatic alcohol, fatty acid, fatty acid amide, fattyamine, rosin amine, alkyl sulfonamide, alkaryl sulfonamide, alkylmercaptan or alkylaryl mercaptan, R' is hydrogen, an alkyl radical offrom 1 to 10 carbon atoms or an aryl radical, R" is hydrogen, an alkylradical of 1 to 10 carbon atoms or an aryl radical, n represents aninteger of from 1 to 150, x represents an integer of 1 to 3, yrepresents an integer of from 0 to 2, and the sum of the integers of xand y is 3.

The phosphate esters of nonionic surfactants useful in attaining theobjects of this invention which are herein contemplated are obtainedfrom precursor nonionic surfactants selected from the group consistingof polyoxyalkylene ethers of organic compounds containing at least 6carbon atoms and having a reactive hydrogen atom and condensed with atleast 1 mole of alkylene oxide. The preferred number of alkylene oxidemolecules reacted with the reactive hydrogen compound may vary from 1 to150 moles and the number of carbon atoms in the alkylene oxide from 1 to12.

In addition to the above described nonionic surfactants, polyoxyalkylenederivatives of organic mercapto compounds such as the products describedin U.S. Pat. No. 2,205,021 (the polyoxyalkylene derivatives of mercaptocompounds such as dodecyl mercaptan, oleyl mercaptan, cetyl mercaptan,benzomercaptan, thiophenols or thionaphthols) may be used. Other usefulpolyalkylene derivatives include the carboxylic acid amides described inU.S. Pat. No. 2,085,706 and the sulfonamides described in U.S. Pat. No.2,002,613. Polyalkylene derivatives of aliphatic organic compounds suchas higher fatty acids and hydroxy fatty acids may also be used.

Phosphate esters derived from the above nonionic surfactants may beprepared by a variety of methods. Numerous methods for the preparationof these esters may be found in many patents and other publications.Various phosphation agents such as phosphorus pentoxide, phosphorusoxychloride, orthophosphoric acid, polyphosphoric acid or the like mayalso be used.

Generally, it is preferred to use the method as disclosed and claimed inU.S. Pat. No. 3,004,056 by Nunn and Hesse and in U.S. Pat. No. 3,004,057by Nunn. Briefly, this method involves reaction of 1 mole of phosphoruspentoxide (P₂ O₅) with from 2 to 4.5 moles of nonionic surfactant undersubstantially anhydrous conditions at temperatures below 110° C. Themethod gives mixtures of mono- and di-substituted phosphate esters.

Another useful method for producing mono- and di-substituted phosphateesters is that disclosed in U.S. Pat. No. 3,277,217. This methodinvolves oxidation of mono- and di-substituted phosphites to thecorresponding phosphates. The method may be used to producemonosubstituted, disubstituted, trisubstituted or mixtures of thesesubstituted phosphate esters in higher states of purity as well asmixtures of these esters in which the concentration of each of the typesof esters may be maintained within close limits.

The above described mono and disubstituted phosphate esters may be usedin this invention in their free and unneutralized form or in the form ofpartially or completely neutralized salts containing as cations, alkalimetals, alkaline earth metals, other metals, ammonia or organic amines.It is to be understood that such salts are to be considered as theequivalents of the phosphate esters in their free form. As examples ofsuitable cations for neutralizing the mono and disubstituted phosphateesters, there may be mentioned sodium, potassium, lithium, calcium,strontium, barium, magnesium, iron, tin, cadmium, aluminum, antimony,chromium, manganese, mercury, nickel, ammonia or organic amines such asthe mono, di, and trimethylamines, ethylamines, propylamines,butylamines, hexylamines, octylamines, decylamines, laurylamines,stearylamines, ethanolamines, propanolamines, butanolamines,hexanolamines, cyclohexylamines, phenylamines, pyridine, morpholine orthe like.

Suitable Pigments

The pigment concentrates of this invention can be prepared with any ofthe wide variety of pigments and colorants that have been proven usefuland effective for use with resinous polymers containing polymerizedconjugated diene monomers, and with K-Resin® resins and similarpolymodal, resinous, linear or branched, block, butadiene/styrenecopolymers. Pigments are currently available to produce a broad spectrumof transparent, opaque, fluorescent, pearlescent, or metallic colors.The pigment should be thermally stable at temperatures at least as highas encountered in blending the pigment concentrate. Generally, suitablepigments include many inorganic compounds, organic compounds and metalflakes, as long as said pigment is thermally stable up to at least about400° F. (204° C.). Thermal instability would result in compositionswhich would be off-color and not true to the desired coloration. Thermalstability can be tested by heating a sample of the pigment, wrapped inaluminum foil to exclude air as much as possible, in a compression moldat say 400° F. (204° C.) for 30 minutes and then examining the samplefor any color change. A significant change in color is indicative ofthermal instability.

Typical classes of inorganic pigments include iron oxides, cadmiumsulfides, molybdates and chromates. Typical classes of organic pigmentsinclude anthroquinones, quinacridones, phthalocyanines, perylenes, andisoindolinones. Typical metallic flakes include copper, aluminum andbrass.

Suitable Resins

The resins to which this invention applies are resinous copolymerscontaining significant amounts of polymerized conjugated diene monomers,i.e., with a diene content in the range of from about 5 to about 40percent by weight based upon the total resin composition, or preferablyin the range of from about 10 to about 30 weight percent.

The resins to which this invention applies further comprise the resinsmarketed as K-Resin® resins, characterized as the linear or branchedblock copolymers of butadiene and styrene disclosed in, e.g., U.S. Pat.No. 3,639,517 to Kitchen et al. The resins are described therein to havestrength, clarity, processability and environmental durability. For manyapplications of these resins, their impact strength is an importantfeature.

A resin useful in accordance with this invention has the generic formula(A-B)_(x) Y, wherein A is essentially a block of polymerizedmonovinyl-substituted aromatic monomers of 8 to about 16 carbon atoms; Bis essentially a polymerized conjugated alkadiene block, the alkadienehaving 4 to about 12 carbon atoms; Y is an atom or group of atomsderived from a polyfunctional coupling agent; and x represents thenumber of functional groups of said polyfunctional coupling agent.

The resins useful in accordance with this invention can be branched.That means more than two blocks A-B are connected via one radical of thepolyfunctional coupling agent.

The preferred weight distribution of A and B is such that the polymercomprises about 70 to about 95 weight percent, more preferably about 75to about 85 weight percent of the polymerized monovinyl-substitutedaromatic hydrocarbon and about 30 to about 5 weight percent, morepreferably about 25 to about 15 weight percent, of the polymerizedconjugated alkadiene monomer.

Presently preferred is the polymodal resin obtained by copolymerizingbutadiene and styrene, coupled by an epoxidized linseed oil having anaverage of about 5 functional groups per molecule. Another preferredpolymer is derived from isoprene and styrene as comonomers. The polymerblocks A-B preferably demonstrate a plurality of nodes on a gelpermeation chromatograph before coupling. Thus, the resulting copolymerhas a polymodal molecular weight distribution. The preferred resins canadditionally be defined as having a melt flow of about 0.5 to about 20.0as determined by ASTM D-1238-65T, Condition G, and when formed into anarticle as demonstrating a haze transmittance in the range of about 0 toabout 20 percent as determined by ASTM D-1003-61, Procedure A, a fallingball impact strength value of at least 1.0 ft.-lbs. and environmentalstress cracking resistance value of at least 100 days at 0 percentfailure.

Polymers useful in the composition of this invention, as well as themethods to make same, are disclosed in more detail in U.S. Pat. No.3,639,517, which is hereby included in this disclosure by reference. Onepresently preferred polymer is a polymodal, branched butadiene/styreneblock copolymer comprising about 24 weight percent butadiene and about76 weight percent styrene. The branches of this radial block copolymerhave a bimodal molecular weight distribution in the styrene blocks.

Other versions of K-Resin® resins, to which this invention is equallyapplicable, are disclosed in U.S. Pat. Nos. 4,091,053; 4,051,197;4,080,407; 4,120,915; 4,104,326; 4,308,364, and 4,309,517, all assignedto Phillips Petroleum Company.

As previously disclosed, this invention is not limited to resinsdescribed as K-Resin® resins in the U.S. patents cited above, but can beapplied to any resinous linear or branched block copolymer comprisingsignificant proportions of a conjugated alkadiene, preferably inconjunction with a vinyl arene. The use of the additives disclosedherein to prepare resinous pigment concentrates comprising portions ofsuch copolymers can be expected to be effective in reducing problems inthe finished colored polymer compositions which can be attributed toinstability in the alkadiene phase of such polymers.

Blending Conditions for Resin Pigment Concentrate Preparation

The resinous pigment concentrate of this invention can be prepared inconventional thermoplastic resin processing equipment. The typicalprocedure involves first adding the naphthenic oil or partial ester ofphosphoric acid to the resin pellets, followed then by the pigment, allunder intensive mixing conditions. A compounding extruder can beconveniently employed as the mixing apparatus. The temperature duringthe mixing operation should not exceed about 450° F. (232° C.) to avoiddegradation of the resin or other components of the pigment concentrate.However, mixing can generally be done effectively at about 400° F. (204°C.).

The polymer compositions comprising the pigment concentrates of thisinvention can also contain small amounts of conventionally employedadditives such as stabilizers, antioxidants, antiblocking agents, andthe like.

The invention and its advantages will be more fully understood from thefollowing example:

EXAMPLE I

Several K-Resin® resin pigment concentrate runs were made which comparedthe effect of dispersing additives of this invention (Runs B and C)against a control run which employed no additive (Run D) and anothercontrol run which employed a white mineral oil (Run A) as the additive.

Each run employed 0.37% by weight of a green pigment which was a blendof carbon black (0.05% by weight), Phthalocyanine Green (0.145% byweight) and azo yellow (0.175% by weight). All the above percent byweight figures are based on the total resin pigment concentratecomposition. Runs A, B, and C each used 2 percent by weight of theadditive while run D used no additive. The balance of each pigmentconcentrate was made up of K-Resin® resin (KR-05). See Example I of U.S.Pat. No. 3,939,112 for a general description of this type of polymer.K-Resin® resin KR-05 is a selected grade of K-Resin® resin KR-03 whereinthe selection is based on a very low "fish eye" (gels) content. TheKR-05 resin is particularly well suited for applications where a highdegree of clarity is desired. However, this invention is not limited tothis particular type and grade of polymer as has been noted earlier. Thepartial ester of phosphoric acid employed in Run B has been previouslydescribed (GAFSTAT®AE-610 ). The naphthenic oil used in Run C wasSunthene 380® (Sun Oil Co.), described earlier herein. The white mineraloil used in Run A was Sontex 350 from Marathon Morco Co. This oil is apetroleum derived, highly paraffinic oil.

Each of the pigment concentrates was made in a pelletizing extruder atabout 400° F. (204° C.) by adding the dispersing additive, then thepigment, to the K-Resin® resin. Each pigment concentrate was blendedwith virgin resin at a 24/1 (virgin/concentrate) let down ratio. Eachblend was then employed to form molded green bottles. The bottles wereexamined for gels, agglomerates and color streaking. The resultsobtained in these runs are shown in Table I.

                  TABLE I                                                         ______________________________________                                               Comment/Rating.sup.a                                                                                 C       D                                       Property A         B (Invention)                                                                            (Invention)                                                                           (Control)                               ______________________________________                                        Agglomerates                                                                           Few/3     Few/2      Few/1   Many/4                                  Streaks  Several/3 Few/1      Few/2   Many/4                                  Gels     Several/3 Few/2      Few/1   Many/4                                  Overall Rank                                                                           3         2          1       4                                       ______________________________________                                         .sup.a Qualitative visual inspection rating.                             

The results shown in Table I show that the addition of the naphthenicoil (Run C) and the partial ester of phosphoric acid (Run B) in theK-Resin® resin pigment concentrate provided a significant reduction inthe problems of gels, pigment agglomerates, and color streaking in thefinal blow molded bottles. Surprisingly, the use of white mineral oil(Run A) in preparing the K-Resin® resin pigment concentrate providedonly a slight improvement over the control run D which employed noadditive, thus illustrating the advantages of the invention additivesused in Runs B and C.

While this invention has been described in detail for purposes ofillustration, it is not to be construed as limited thereby, but isintended to cover all changes and modifications within the spirit andscope thereof.

I claim:
 1. A resinous pigment concentrate comprising a major portion ofa resinous polymer containing at least one polymerized conjugated dienemonomer in proportions in the range of from about 5 to about 40 weightpercent, based upon the total resinous polymer; a minor portion of atleast one pigment, and a dispersing additive consisting essentially of anaphthenic extender oil.
 2. A resinous pigment concentrate in accordancewith claim 1 wherein said naphthenic extender oil is present in anamount in the range of from about 0.5 to less than 2 weight percent ofsaid pigment concentrate.
 3. A resinous pigment concentrate inaccordance with claim 2 wherein said pigment is present as at leastabout 0.01 weight percent of the total pigment concentrate.
 4. Aresinous pigment concentrate in accordance with claim 1 wherein saiddispersing additive is present as an amount in the range of from about 2to about 12 weight percent of said concentrate, and said pigment ispresent as at least about 2 weight percent of said concentrate.
 5. Aresinous pigment concentrate in accordance with claim 1 wherein saiddispersing additive is present in an amount effective to prevent theformation of gels or blemishes in articles produced of resins coloredwith said pigment concentrate.
 6. A resinous pigment concentrate inaccordance with claim 1 wherein said naphthenic extender oil comprisesnaphthenes, paraffins, aromatic hydrocarbons and mixtures thereof, andhas a viscosity in the range of from about 100 to about 5000 SUS at 100°F.
 7. A resinous pigment concentrate in accordance with claim 1, whereinsaid naphthenic extender oil consists essentially of from about 30 to 50weight percent naphthenics, from about 35 to 55 weight percentparaffins, and from about 5 to about 25 weight percent aromatics, thetotal being 100 weight percent.
 8. A resinous pigment concentrate inaccordance with claim 1 wherein said naphthenic extender oil is ASTMD-2226 Type
 103. 9. A resinous pigment concentrate in accordance withclaim 1 wherein said pigment is selected from the group consisting ofmetals and organic and inorganic compounds which are thermally stable attemperatures at least as high as the maximum mixing temperature of saidresinous pigment concentrate.
 10. A resinous pigment concentrateprepared by a process comprising the following steps:(a) under intensivemixing conditions, blending with a major portion of a resinous copolymercontaining at least one polymerized conjugated diene monomer inproportions in the range of from about 5 to about 40 weight percent,based upon the total resinous copolymer, an amount of a naphthenicextender oil as a dispersing additive effective to reduce gel formationor surface blemishes in finished articles made of a polymer which iscolored with said resinous pigment concentrate; and (b) adding at leastone pigment to said major portion of resinous polymer and said minorportion of naphthenic oil, as at least about 0.1 weight percent of saidresinous pigment concentrate.
 11. A process of preparing coloredresinous copolymers containing at least one polymerized conjugated dienemonomer in proportions in the range of from about 5 to about 40 weightpercent, based upon the total resinous copolymer, which comprises theblending of said resinous copolymer under intensive mixing conditionswith a resinous pigment concentrate comprising a major portion of aresinous pigment concentrate comprising a major portion of a resinouscopolymer containing at least one polymerized conjugated diene monomerin proportions in the range of from about 5 to about 40 weight percentof said copolymer, a minor portion of at least one pigment, and adispersing additive consisting essentially of a naphthenic oil. 12.Colored resins prepared in accordance with claim
 11. 13. Articles ofmanufacture prepared from colored resins prepared in accordance withclaim
 11. 14. Articles of manufacture in accordance with claim 12prepared in the form of films, sheets, or blow moldings.
 15. A resinouspigment concentrate prepared in accordance with claim 10 wherein saidresinous copolymer is a polymodal linear or branched block copolymerhaving the generic formula (A-B)_(x) Y, wherein A is essentially a blockof polymerized monovinyl-substituted aromatic monomers having from 8 toabout 16 carbon atoms; B is essentially a polymerized conjugatedalkadiene block, the alkadiene having from 4 to about 12 carbon atoms; Yis an atom or group of atoms derived from a polyfunctional couplingagent; and x represents the number of functional groups of saidpolyfunctional coupling agent.
 16. A process in accordance with claim 11wherein said copolymers have the generic formula (A-B)_(x) Y, wherein Ais essentially a block of polymerized monovinyl-substituted aromaticmonomers having from 8 to about 16 carbon atoms; B is essentially apolymerized conjugated alkadiene block, the alkadiene having from 4 toabout 12 carbon atoms; Y is an atom or group of atoms derived from apolyfunctional coupling agent; and x represents the number of functionalgroups of said polyfunctional coupling agent.